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. H. WALKER & G. EASTMAN.

FLEXIBLE PHOTOGRAPHIG FILM.

No. 420,130. Patented Jan. 28,1890

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a s1 Y I \E u 5= WITNEEEE5= N W M I WMWMQD ilnrrnn STATES PATENT OFFICE.

WILLIAM H. AND GEORGE EASTMAN, OF ROCHESTER, NEW YORK, ASSIGNORS, BY MESNE ASSIGNMENTS, TO THE EASTMAN DRY PLATE AND FILM COMPANY, OF SAME PLACE.

' FLExueuz PHOTOGRAPHIC FILM.

SPECIFICATION forming part of Letters Patent No. 420,130, dated January 28, 1890. Application filed June 2'], 188' Serial No. 136,132. (No model.)

' To all whom it may concern: V

' Be it known tha-twe,WILLIAM H. WALKER and GEORGE EASTMAN, citizens of the United States, residing at Rochester, in the county 5 of Monroe, in the State of New York, have jointly invented certain Improvements in Flexible Photographic Films, of which the following is a specification,

had to the accompanying drawings. Our invention relates to certain improvements on the inventions described in the patents of George Eastman, (one of the present joint inventors) No. 306,594., dated October 14, 1884, and of George Eastman and William H. Walker, (the present applicants,) No.

306,470, dated October 14, 188i, which improvements are fully described in the following specification, and the nov'el features th ereof specified in the claim hereunto annexed.

Our present improvements in photography are illustrated in the accompanying drawings, in which-:

Figures 1 and 2 are sections on an enlarged scale th rou gh our improved photographic films 2 5 embodying the inventions herein described.

In the practical operations of producing our improved photographic films embodying the inventions claimed herein, we take any suitable paper A, Figs. 1 and 2, and apply to one side thereof by any suitable means a coating or layer of soluble gelatine B. We prefer to use those kinds of paper known in thephotographictradeas Saxe or Rives, on account of their freedom from chemical 3 5 impurities and the evenness of their texture; but other brands of paper may be employed. The gelatine is dissolved in water in the proportion of about fifty grains to the ounce, the exact proportions being not very material, 40 depending somewhat on the temperature of the atmosphere and the means by which the paper is coated, the object being to cover the paper with a thin uniform layer of gelatine. Any suitable gelatine may be employed that will not ,dissolve in water at ordinary temperatures; but we prefer to use Nelsons No. l or a mixture of Nelsons No. 1 and Simeons hard gelatine in abou Lequal proportions. The paper support may be coated by hand by reference being any suitable device, or by floating the support on the solution of gelatine; but we prefer to employ mechanism which we have invented for this purpose, and which mechanism we design to make the subject of a sepa rate application for Letters Patent.

As the next step in the preparation of our improved photographic films, we pass the paper support coated with the layer of soft gelatine after drying through a suitable set ofcalender-rolls, by which the support and coa in g are compressed and hardened and the surface of the gelatine layer or substratum is smoothed or polished and rendered more suitable for the subsequent operations. The calendered support and substratum A andB are then coat-ed on the surface of-the substratum with another layer C, which consists of gelatine rendered insoluble by the addition thereto of chrome-alum or other suitable chemical, or by a layer of plain collodion or shellac or other suitable gum dissolved in alcohol or spirits, the obj ectof this second coating being to isolate the emulsion film D from the soluble-substratum B and to improve the surface on which the emulsion is coated. The gum or collodion layer 0 may be applied by floating on the surface of the solution or by hand or by machinery, in any preferred manner. The coated support is then again allowed to dry. If the second coating consists of gelatine, it may be of a strength of about fifty grains to the ounce of water and one-half grain of chrome-alum. We prefer to use insoluble gelatine-for the second coating on account of its being cheaper. The support provided with the double coating may be again calendered, (and we prefer to do S0,) after which it is ready to receive the coating of the sensitive gelatino-argentic emulsion D. The coated and calendered support is now covered with a layer of sensitive gelatino-argentic emulsion, the preparation of which is now too well known. to require description here. The emulsion is spread evenly over the support in any suitable way, by hand or machinery, and after it has been dried thereon our improved photographic films are ready able 'ing of a quicker z scones chrome-alum or other suitas described in the beforernenti W ications, and all the operations of exposure, development, and the separation of the film containing the image from the support be conducted in the same way as indicated in the said previous applications.

in the practical operation of preparing emulsions on a manufacturing scale, and especially "with some formulas, it frequently happens that the finished emulsion is too thin to giro sufficient body-with a single coat, in which case We applya second coating of emul-' sion (see D 2) after the first has dried. Thesccond coating of emulsion also enables us to modiiy the chemical effects-as, for instance when the first coating of emulsion proves too slow, the sensitiveness of the film may be increased byapplying another coatemulsion, which may be quite thin or dilute. The first coating in this case gives the requisite printing density, while the second imparts the requisite sensitiveness to light.

Glycerine maybe employed in any of the coatings into which gelatine enters as a base, in order to give aceriain amountof flexibility to the completed film. The proportion of glycerine may be varied, the flexibility increasing with the quantity employed; but about two or three per cent. of it added to the bulk of the coating solution will answer the purpose.

The double coating of emulsion may be applied to a flexible support provided with a single layer of the substratum, as described in the applications hereinbefore mentioned.

The interposition of the layer C of relatively less soluble gelatine or of a suitable gum isolates and separates the emulsion layer D from the soluble gelaiine coat B and overcomes a diliiculty which We have sometimes encountered in coating the support with mnuislons made from sonic smnplcs of gelaby treatm nt and the surface of this second coating is much improved and rendered more suitable for the application of the emulsion thereto by the calendering, which polishes and smooths it and renders the layer of the emulsion more uniform.

The object sought by employing a double substratumor two layers between the support and the emulsion film-that is, the improvement of the surface and the filling 11 p of any irregularities inthe paper-may be attained by the use of two coatings of soluble gelatine, either .or both of which may be cal endered when dried. The only objcersought' in rendering the second coating 0 in any de gree insoluble is to prcventits being softened by the application of the emulsion. W'ith emulsions which can be coated at a low temperature it is unnecessary to harden the second coat 0.

The double coating with emulsion renders our improved photographic films more substantial and less rcadilyinjured by handling, and greatly facilitates the process of removal from the support, besides enabling us to overcome the objections already mentioned arising from thin emulsions or from those deficient in sensitivenes We claim- As an improvement in the art of photogn pby, the herein-described sensitive flexible film, consisting of a flexible support A and a layer of sensitized gelatine emulsion D, attached to the support by a coating 13 of relatively more soluble gelatine, and an inter posed layer of insoluble material C, substantially as and for the purposes set forth.

' WM. H. WALKER.

GEORGE EASTMAN. Witnesses:

Gannon B. SELDEN, F. B. HUTCHINSON. 

